Over One-Sixth of America's Coastline Is Under High Threat of Washing Out

There's the US Coast Guard, with its cutter boats and maritime aircraft maintaning law and order along America's coasts. And then there's the US coast guard, with its wetland habitats, vegetation, and reefs forming a barrier to the effects--say, rising sea levels--of climate change. If the threat of being completely washed out doesn't bode well (it doesn't) for America's coasts, its residents still have this other coast guard, the natural one, to thank for shielding lives and property from flooding and walloping weather. That plush beachfront pad may be among the safest places to live.

The rub? It's only if the natural line of defense along America's coasts remains in tact that coastal cities could shield people from sea-level rise, erosion, and vicious superstorms.

That’s according to new research published in Nature Climate Change. The Stanford University study illustrates that existing coastal environments are key to sparing both residents and property from the rising waters levels and walloping storms brought on by rising global temperatures. The flip side is that removing reefs, marshes, mangroves, forests, and other natural ecosystems could put coastal cities at a higher risk of being washed off the map.

The Stanford researchers behind the study built a computer model of coasts in the continental United States and looked at population statistics, residential property values, natural defenses, and the chance of flooding on a scale of one square kilometer. What they found is that 16 percent of America's coastline is considered a high-hazard area, affecting some 1.6 million people. For perspective, that includes 250,000 elderly residents, 30,000 families below the poverty line, and $300 billion in residential property value.

“The number of people, poor families, elderly, and total value of residential property that are most exposed to hazards can be reduced by half if existing coastal habitats remain fully intact,” the study says. “Coastal habitats defend the greatest number of people and total property value in Florida, New York, and California.”

It's estimated that about 67 percent of the coastline is protected by natural barriers, but if the ecosystems are removed the amount of people and property at risk of flooding and other dangers doubles. Many places are already at risk, with natural barriers having been striped away or degraded over time. Some restoration efforts are turning to artificial methods like dune and man-made reefs to build back the coast guard both here and abroad. In the United Arab Emirates, for example, developers have been creating artificial reefs to provide sanctuary for fish and flood protection. However, problems often arise quickly due to financial complications or design issues.

"Although engineered solutions are necessary and desirable in some contexts, they can be expensive to build and maintain," the study adds, "and construction may impair recreation, enhance erosion, degrade water quality and reduce the production of fisheries."

Take one project in Florida that involved blanketing two million old tires across the ocean floor. The tires were dumped in Fort Lauderdale waters in 1972 to create a fake reef comparable in size to 31 football fields. The whole thing backfired, resulting in water and land pollution and the destruction of nearby natural reefs. That's not to drown out projects aimed at both creating artificial barriers between the sea and the land and preserving natural barries, of course. But for now, the other coast guard has to keep holding its breath.